Structures and methods to reduce maximum current density in a solder ball

ABSTRACT

Structures and methods to reduce maximum current density in a solder ball are disclosed. A method includes forming a contact pad in a last wiring level and forming a plurality of wires of the contact pad extending from side edges of the contact pad to respective ones of a plurality of vias. Each one of the plurality of wires has substantially the same electrical resistance.

FIELD OF THE INVENTION

The invention generally relates to semiconductor devices, and moreparticularly to structures and methods for enhancing electromigration(EM) performance in solder bumps and related structures.

BACKGROUND

Integrated circuits conventionally comprise a substrate, semiconductordevices, and wiring (e.g., metallization) layers formed above thesemiconductor devices. The wiring layers comprise various interconnectsthat provide electrical connections between the devices and externalconnections. Solder projections (also referred to as solder bumps,bumps, or solder balls) are commonly utilized to provide a connectionbetween the last (e.g., top) wiring level of a semiconductor device andanother device. A common type of solder bump is the controlled collapsechip connection (C4) solder bump.

Current generation chip products make use of an aluminum last-metal (LM)pad which connects to a C4 solder bump. There are two primary variationson this structure. On the one hand, in structures used specifically forbase silicon-on-insulator (SOI) technologies, the aluminum levelcomprises only a pad (i.e., no wires or other structures), the padmaking a connection directly down through a large, centrally located viaopening to the last metal wiring level (e.g., wire, interconnect, etc.).On the other hand, in conventional structures used for foundry andapplication specific integrated circuit (ASIC) technologies, thealuminum level comprises a combination pad and aluminum last-metalwiring level. The pad in the latter case makes contact to the last metalwiring level through multiple small vias, which are offset in locationwith respect to the pad center (e.g., by about 10 μm). However, in bothinstances, the pad contacts the ball limiting metallization (BLM) layer(also known as the under bump metallization, i.e., UBM) in a singlelarge contact area.

As dimensions of features (e.g., pads, wires, interconnects, vias, etc.)continue to shrink to create smaller devices, the maximum allowablecurrent density decreases rapidly due to electromigration (EM) effects.Electromigration is a well known phenomenon in which, generallyspeaking, atoms of a metal feature are displaced due to the electricalcurrent passing through the feature. The migration of atoms can resultin voids in the feature, which can increase electrical resistance orcause failure of the feature, both of which negatively impactreliability of the integrated circuit. For example, in C4 solder bumpcontact arrangements, electromigration damage typically originates at alocation of highest current density and then progresses across theinterface between the solder bump and the BLM until the connection isbroken.

For conventional technologies, C4 solder bump electromigrationperformance is approaching a performance limit, especially as thetechnologies migrate to lead-free C4 solder structures that are moresusceptible to electromigration. In conventional C4 solder bump contactdesigns, the electrical current pools (e.g., becomes crowded), whichresults in a localized increase in current density. For example, in theknown pad arrangements discussed above, current tends to pool at a smallarea of the leading edge of the connection between the wire, pad, BLM,and solder bump. Particularly, in many applications, nearly all of thecurrent flows through a narrow region at the leading edge of the via,and very little current flows through the remainder of the via. Thiscrowding of current associated with C4 pad and/or via structures oftenresults in electromigration void formation, which can lead to increasedresistance and ultimately failure of the device.

Accordingly, there exists a need in the art to overcome the deficienciesand limitations described hereinabove.

SUMMARY

In a first aspect of the invention, there is a method of forming asemiconductor device. The method includes forming a contact pad in alast wiring level and forming a plurality of wires of the contact padextending from side edges of the contact pad to respective ones of aplurality of vias. Each one of the plurality of wires has substantiallythe same electrical resistance.

In another aspect of the invention, there is a method of forming asemiconductor device. The method includes forming a solder bump contactpad in a last wiring level of a chip and forming at least one wire inthe last wiring level, wherein the at least one wire contacts thecontact pad. The method also includes forming a dielectric capping layeron the last wiring level, the contact pad, and the at least one wire,and forming an opening in the dielectric capping layer, wherein theopening exposes a portion of an upper surface of the contact pad anddefines at least one block. The at least one block comprises residualmaterial of the dielectric capping layer on a portion of the contact padsurrounding a location where the at least one wire contacts the contactpad.

In another aspect of the invention, there is a method for forming asemiconductor device. The method includes forming a capping layer on asolder bump contact pad that is arranged in a last wiring level of achip, and forming a passivation layer on the capping layer. The methodalso includes forming a terminal via in the capping layer, wherein theterminal via contacts the contact pad, and forming a final via in thepassivation layer, wherein the final via is in electrical contact withthe terminal via. The method also includes making upper surfaces of thefinal via and the passivation layer co-planar, forming a ball limitingmetallurgy (BLM) layer on the co-planar upper surfaces of the final viaand the passivation layer, and forming a solder bump on the BLM layer.

In another aspect of the invention, there is a method of forming asemiconductor device. The method includes forming at least one terminalvia in a capping layer, and planarizing upper surfaces of the at leastone terminal via and the capping layer. The method also includes forminga passivation layer on the planarized upper surfaces of the at least oneterminal via and capping layer, and forming at least one final via inthe passivaiton layer. The method further includes forming a balllimiting metallurgy (BLM) layer on upper surfaces of the at least onefinal via and the passivation layer, and forming a solder bump on theBLM layer.

In another aspect of the invention, there is a semiconductor structureincluding a contact pad in a last wiring level of a chip and a pluralityof wires of the contact pad extending from side edges of the contact padto respective ones of a plurality of vias. Each one of the plurality ofwires has substantially the same electrical resistance. A first one ofthe plurality of wires has a first length and a first width. A secondone of the plurality of wires has a second length and a second width.The first width is different from the second width and the first lengthis different from the second length.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIGS. 1 and 2 show solder bump contact arrangements;

FIG. 3 shows a map of current density in a contact pad;

FIGS. 4 and 5 show solder bump contact configurations according toaspects of the invention;

FIG. 6 shows a map of current density in a contact pad according toaspects of the invention;

FIG. 7 shows a top-down view of a semiconductor structure in accordancewith aspects of the invention;

FIGS. 8A, 8B, 9A, 9B, 10A, and 10B show structures and respectiveprocessing steps in accordance with aspects of the invention;

FIGS. 11-13 show partial perspective views of semiconductor structuresin accordance with aspects of the invention;

FIGS. 14-51 show semiconductor structures and respective processingsteps of a solder bump contact arrangement in accordance with aspects ofthe invention; and

FIG. 52 is a flow diagram of a design process used in semiconductordesign, manufacture, and/or test.

DETAILED DESCRIPTION

The invention generally relates to semiconductor devices, and moreparticularly to structures and methods for enhancing electromigration(EM) performance in solder bumps and related structures. In embodiments,a contact pad in a last wiring level is configured to distribute currentamong plural same-resistance wires leading into plural vias under asolder bump. In additional embodiments, current in a contact pad isdiverted using one or more blocks of insulating material that cause thecurrent to spread out within the contact pad. In further embodiments,conductive structures between the contact pad and the solder bump areconfigured to spread current using configurations of copper structures,by planarizing levels, and by eliminating the conventional aluminum pad.In this manner, implementations of the invention provide improved EMresistance by reducing current density in solder bump contactarrangements.

FIG. 1 shows a cross sectional view of an exemplary semiconductorstructure in which layer 10 is an upper level (e.g., last level, lastmetal, LM, etc.) wiring layer of an integrated circuit chip. Layer 10 isformed atop one or more additional wiring levels of the chip (not shown)and may be composed of, for example, dielectric material, e.g., dopedsilicon carbide, silicon nitride, low-k materials, TEOS, FTEOS, etc. Acontact pad 12 is disposed in the layer 10 and is electrically connectedto one or more wires 15 also disposed in the layer 10, the wires 15representing back end of line (BEOL) wiring of the chip. The contact pad12 is formed around discrete posts 17 of the material of the layer 10,such that the contact pad 12 is perforated (or ‘cheesed’), as is knownsuch that further explanation is not believed necessary for a completeunderstanding of the invention.

The contact pad 12 and wires 15 may be composed of any suitableconducting material, including, but not limited to: copper, copperalloy, aluminum, etc. The contact pad 12 and wires 15 may be formed inthe layer 10 using conventional semiconductor processing techniques,such as, for example, masking and etching the layer 10 in a prescribedpattern, e.g., using photolithography and reactive ion etch (RIE), anddepositing conductive material in the etched portions of the layer 10,e.g., using chemical vapor deposition (CVD), plasma enhanced chemicalvapor deposition (PECVD), atomic layer deposition (ALD), etc.

Formed over the layer 10 is capping layer 20 of hard dielectric. Thecapping layer 20 comprises two films 22 and 23, the lower film 22 beingcomposed of an oxide based material, and the upper film 23 beingcomposed of a nitride based material. The capping layer comprises aterminal via (TV) opening 25 centered over the contact pad 12. Aconductive pad 30, which is commonly composed of aluminum, is formed onthe capping layer 20 and on the layer 10 and contact pad 12 in theterminal via opening 25. A passivation layer 35 having a final via (FV)opening 40 is formed over the pad 30. The passivation layer 35comprises, for example, photosensitive polyimide (PSPI).

Still referring to FIG. 1, the semiconductor structure further includesa ball limiting metallization (BLM) layer 45 and a solder bump 50. TheBLM layer 45 is arranged along exposed portions of a final via opening40 formed in the passivation layer 35. The pad 30 may be composed ofaluminum, the BLM 45 may be composed of at least one of tungsten,copper, and nickel, and the solder bump 50 may comprise a conventionallead free composition (e.g., tin, copper, etc.). The contact pad 12,aluminum pad 30, and BLM layer 45 provide a conductive path between thewires 15 and the solder bump 50.

FIG. 2 shows a plan view of the contact pad 12 and the posts 17, thecontact pad 12 being substantially centered relative to the terminal viaopening 25 and the final via opening 40. For advanced technology nodes,the contact pad 12 may be substantially rectangular with a width ofabout 46.4 μm and a height of about 18.4 μm. The posts 17, which areuseful for preventing dishing of the contact pad 12 during chemicalmechanical polishing (CMP) are also substantially rectangular, having awidth of about 6.16 μm and a height of about 2.92 μm. Also for the 45 nmtechnology node, the terminal via opening 25 is substantiallyrectangular having a width of about 44 μm and a height of about 16 μm,and the final via opening 40 is substantially circular having a diameterof about 58 μm.

FIG. 3 shows a plot of current density (e.g., a current density map) inthe contact pad 12. Area 55 depicts a relatively high current density atthe leading edge of the contact pad 12 where the current initiallyenters the contact pad 12, whereas area 60 depicts a relatively lowcurrent density at other portions of the contact pad 12. The highcurrent density at the leading edge of the contact pad 12 can result inan origination of electromigration damage, which can ultimately lead tofailure of the chip. Moreover, the formation of the relatively largefinal via opening 40, described above, can produce undesired mechanicalstress in the BEOL layers of the chip beneath the solder bump.

FIG. 4 shows a contact pad 100 in accordance with aspects of theinvention. In embodiments, the contact pad 100 is disposed in a lastmetal layer (e.g., similar to layer 10 of FIG. 1) and is divided intoseveral discrete wires 105 a, 105 b, . . . , 105 n. Each wire isconnected between an edge 110 of the contact pad 100 and one of aplurality of vias 115 a, 115 b, . . . , 115 n that extend from the lastmetal layer to a next layer above. The dimensions of the respectivewires 105 a, 105 b, . . . , 105 n are selected such that each wireprovides substantially the same resistance between an edge 110 of thecontact pad 100 and the respective vias 115 a, 115 b, . . . , 115 n,such that the current to each of the vias 115 a, 115 b, . . . , 115 n isthe same. By diverting the current amongst plural wires and vias, thecurrent is divided up and forced to flow through separate locationswithin a final via opening 119 (which may be similar to final viaopening 40 described in FIG. 1). In this manner, a magnitude of the peakcurrent density is reduced relative to that for arrangements thatutilize a single large via (e.g., such as that described with respect toFIGS. 1-3).

In embodiments, the width and length of each one of the wires 105 a, 105b, . . . , 105 n are adjusted to produce the same electrical resistancebetween the edges 110 of the contact pad 100 to the individual vias 115a, 115 b, . . . , 115 n. More specifically, by forming each of the wires105 a, 105 b, . . . , 105 n with a common thickness (e.g., the depth ofthe last metal layer) and of a same material (e.g., having the sameresistivity), the resistance for a particular wire may be selectivelyadjusted based on the length and width of the wire. Particularly, whenthickness and resistivity are common amongst the wires, a relativemeasure of the resistance of each wire may be approximated by the ratioof length to width of a wire.

As an illustrative non-limiting example, wire 105 d may be composed oftwo segments 120 and 121. Segment 120 may have a length of about 7 μmand a width of about 1.2 μm, and segment 121 may have a length of about1.5 μm and a width of about 2.4 μm. A relative measure of the resistanceof the wire 105 d is given by the sum of (7 μm/1.2 μm) and (1.5 μm/2.4μm), which equals about 6.5 squares of metal. Similarly, wire 105 b maybe composed of two segments 125 and 126. Segment 125 may have a lengthof about 13 μm and a width of about 2.18, and segment 126 may have alength of about 2 μm and a width of about 4 μm. The relative measure ofthe resistance of the wire 105 b is given by the sum of (13 μm/2.18 μm)and (2 μm/4 μm), which equals about 6.5 squares of metal. Thus, althoughwires 105 d and 105 b have different shapes, the wires 105 a and 105 bhave substantially the same resistance and therefore deliver the sameamount of current to their respective vias 115 d and 115 b. It is notedthat the dimensions described herein are merely exemplary and are notintended to limit the invention. Instead, any number of wires having anydesired geometry may be used within the scope of the invention, providedthat the wires have substantially the same resistance, as describedherein. For example, FIG. 5 depicts another exemplary layout of wires105 a-n and vias 115 a-n in accordance with aspects of the invention.

In embodiments, each wire 105 a, 105 b, . . . , 105 n increases in width(e.g., the wire diverges) immediately in front of the one of the vias115 a, 115 b, . . . , 115 n to which it is connected. This allowscurrent spreading in order to produce a more uniform currentdistribution along the leading edge of the via. In particularembodiments, each wire (e.g., 105 d) has a maximum width within one viawidth from a leading edge of the via (e.g., 115 d) to allow for currentfan-out (e.g., divergence) to the leading edge of the via.

In accordance with aspects of the invention, the size and location ofeach respective via 115 a-n may be selected according to a desiredconfiguration for the solder bump contact arrangement. Althoughparticular via sizes are shown in FIGS. 4 and 5 (e.g., via 115 d in FIG.4 has a footprint of 3 μm by 3 μm), the invention is not limited to viasof any particular size. Instead, any desired size vias may be usedwithin the scope of the invention. The contact pad 100 including wires105 a-n and vias 115 a-n may be formed in a layer using conventionalsemiconductor processing techniques, such as, for example, masking andetching the layer in a prescribed pattern, e.g., using photolithographyand reactive ion etch (RIE), and depositing conductive material in theetched portions of the layer, e.g., using CVD, PECVD, ALD, etc.

In embodiments, the layout of a contact pad 100 may be configured to bein conformance with design rules, such as, for example, minimum wirewidth (e.g., 0.8 μm), minimum spacing between wires (e.g., 0.8 μm),minimum via size (e.g., 3 μm by 3 μm), and maximum amount of metaldensity in a given area (e.g., 75%), etc. For example, a layout of acontact pad 100 including the number of a wires and vias, and relativesizes and spatial distribution of the wires and vias, may be determined(e.g., using numerical optimization techniques) to maximize the numberof wires and vias (e.g., for dividing the current) while satisfying theconstraint of each wire having substantially the same electricalresistance and while also satisfying any applicable design rules for themanufacturing technology. Although particular examples of design ruleshave been described herein, the invention is not limited to these designrules; rather, any suitable design rules may be used within the scope ofthe invention.

FIG. 6 shows a current density map 120 within the several vias 115 a-nfrom the contact pad 100 depicted in FIG. 4. When compared to thecurrent density map of the contact pad 12 shown in FIG. 3, it can beseen that the contact pad 100 made in accordance with aspects of theinvention spreads the current to more locations within an final via andsolder bump. In this manner, implementations of the invention reduce theeffects of EM damage in the solder bump contact arrangement.

However, even with plural wires and vias, as described in accordancewith aspects of the invention, the current flows through less than halfthe footprint of each respective via, meaning that the current pools(e.g., crowds) at the leading edge of each respective via. Accordingly,in embodiments, the width of each respective via (e.g., measuredperpendicular to the leading edge of the via) may be minimized to thedesign rule minimum. For example, a layout of a contact pad includingthe number of a wires and vias, and relative sizes and spatialdistribution of the wires and vias, may be determined to maximize thenumber of wires and vias while satisfying the following constraints:each wire having substantially the same electrical resistance;minimizing the width of each respective via; and, satisfying anyapplicable design rules for the manufacturing technology.

In embodiments, by using plural vias and wires having substantially thesame resistance, any EM damage that occurs at a particular via isconfined to that via and does not propagate to affect another via. Forexample, if EM damage begins at a particular via and eventually destroysthe connection between that via and the BLM, the damage is confined tothat particular via while the other vias remain unaffected by the damageand continue carrying current.

By providing a contact pad with plural wires and vias, where each wirehas substantially the same resistance, implementations of the inventioncause the current arriving at an edge of the contact pad to bedistributed amongst plural locations in the final via and solder bump.This reduces the amount of near-zero current density areas (e.g., area60 shown in FIG. 3), which allows the contact pad 100 made in accordancewith aspects of the invention to be smaller than contact pad 12 shown inFIGS. 1-3. As such, by using plural distributed vias and same resistancewires in accordance with aspects of the invention, the FV openingdiameter may be reduced, which reduces stress on the underlying layersof the chip. In a particular non-limiting example, the FV openingdiameter used with a contact pad 100 in accordance with aspects of theinvention is about 30 μm, while the FV opening diameter used with aconventional contact pad that carries about the same amount of currentis about 47 μm. Thus, implementations of the invention reduce currentdensity by better distributing the current within the FV and solderbump, and also provide for a smaller FV opening diameter which reducesundesired stress in underlying layers of the chip.

In embodiments, a contact pad in accordance with aspects of theinvention comprises a last-metal (LM) layer connection structure formedhaving an overall footprint (e.g., overall length by width) similar toor smaller than a conventional last-metal copper pad structure on an ICchip. The contact pad provides current distribution between the LM layeron the IC chip and a connecting solder bump, and is configured to directthe current into a circular central area of the solder bump connectionthrough multiple individual via connections between the LM layer and thesolder bump. The contact pad and the vias are positioned to provide arelatively uniform current distribution within the central area of thesolder bump. The contact pad and each via in a dielectric layeroverlying the LM layer define where the current enters the bottom of thesolder bump and limits the extent of EM damage at that location (e.g.,limits EM damage associated with that via to that via). Additionally,the wires in the LM layer that connect to the contact pad may beconstrained to the width of the contact pad and connect only at theopposite ends of the contact pad without looping out to contact thesides of the contact pad.

In embodiments, the contact pad has multiple internal wires of differentand varying widths and lengths connected to respective vias. The widthand length of each wire may be tailored to provide similar resistancevalues between the edge of the pad and a respective via within a centralportion of the contact pad. Moreover, a wire may have more than onewidth along its length, and the wire may have a maximum width within onevia width in front of the edge of the via (e.g., to allow current fanoutto the leading edge of the via).

In accordance with additional aspects of the invention, a patternedinsulator may be used to reduce current density by diverting anddistributing current flowing from a contact pad to an upper levelconductor pad. The patterned insulator may be used in addition to, oralternatively to, arranging the geometry of the contact pad as describedabove with respect to FIGS. 4-6.

FIGS. 7-13 show exemplary arrangements of wires, contact pads, andblocks (e.g., current blocking structures) in accordance with aspects ofthe invention. However, the invention is not limited to the exemplarygeometries of the features (e.g., wires, contact pad, blocks, conductivelayers, etc.) described with respect to FIGS. 7-13. Instead, a contactpad may have any desired shape within the scope of the invention, andany number of wires and blocks having any desired shapes may be usedwithin the scope of the invention. By using implementations of theinvention, such as those described with respect to FIGS. 7-13, the LMlayer under the solder bump (e.g., solder ball) is designed to redirectthe electron current vector at the target metal interface to aprescribed angle range while maximizing pinch volume length (where pinchvolume represents a volume at the solder-barrier-LM interface where thedistance between a point in the solder axis and a point in the currentfeed LM line is less than a given value). Accordingly, current vectorswithin the pinch volume point away from the solder axis and/or areparallel to each other, which is different from conventionalarrangements in which current vectors point towards solder axis. In thismanner, electrical connectivity between the LM layer and the solder istailored to manipulate current vectors in the pinch volume, and wires inthe LM layer with equal current density can be merged at a point ofequal potential relative to a point in the solder axis.

As described herein, C4 electromigration (EM) capability is limited bycurrent crowding in final pad/via designs. Known designs commonly employa last metal (LM) layer copper wire that introduces current laterallybelow the UBM/C4 bump structure, and up into the UBM/BLM through a harddielectric (e.g., capping layer) terminal via (TV) opening and abovethat through a top-level polyimide final via (FV) opening. There istypically a layer of aluminum (e.g., an aluminum pad) disposed betweenthe hard dielectric and polyimide layers, the layer of aluminum servingas a pad support layer for the UBM/BLM/C4 structure. Current exiting thelast metallization (LM) layer flows directly through the UBM/BLM intothe solder bump. Due to the normally thin dimension of the last metalwiring (e.g., on the order of about 1 μm), the current enters the solderconcentrated at the edge of either the terminal via or the final via.Thus, the current density is very high where the current enters thesolder, and much lower elsewhere in other portions of the conductivematerial. The result of this non-uniform current distribution is that EMdamage first occurs at the location of highest current density. Once theEM damage begins, voiding in the solder bump or the UBM follows shortly,and the location of the high current density moves to the edge of thevoid, widening the damage area.

FIG. 7 shows a top-down partial view of a solder bump contactarrangement in accordance with aspects of the invention. Thisarrangement includes a contact pad 212 and wires 215, both shown indashed lines. A TV opening 217 is formed in a capping layer formed overthe contact pad 212 and exposes a portion of the contact pad 212. The TVopening 217 is shaped such that a portion of the capping layer forms ablock 220 over a portion of the contact pad 212, where the wire 215connects to the contact pad 212. In embodiments, the wire 215 may besimilar to wire 15 described with respect to FIG. 1, and the contact pad212 may be similar to contact pad 12 described with respect to FIG. 1and/or contact pad 100 described with respect to FIGS. 4 and 5.

In embodiments, the block 220 is formed from residual material of acapping layer (e.g., which may be similar to capping layer 20 of FIG. 1)that is patterned and left in place during formation of the TV opening217 (e.g., which may be similar to TV opening 25 of FIG. 1). Accordingto aspects of the invention, the block 220 is sized and located over aportion of the contact pad 212 where the wire 215 enters the contact pad212. When viewed in plan view (e.g., top down view), the block 220surrounds the location of the contact pad 212 where the wire 215 comesinto contact with the contact pad 212. When the next conductive layer(e.g., pad 30 from FIG. 1) is formed over the contact pad 212 in the TVopening 217, the block 212 obstructs (e.g., prevents) direct contactbetween the next conductive layer and the contact pad in the areadefined by the block 212. In this manner, current coming into thecontact pad 212 through the wire 215 cannot turn immediately upward whenit reaches the contact pad 212, but rather must travel through thecontact pad 212 beyond the extent of the block 220 before moving upwardto the next conductive layer. Accordingly, the block 220 re-directs(e.g., diverts) the incoming current, shown by arrows “A”, into a largerarea of the contact pad 212, which reduces current density and,therefore, minimizes EM effects.

FIGS. 8A, 8B, 9A, 9B, 10A, and 10B depict structures and processingsteps in accordance with aspects of the invention. FIGS. 8A, 9A, and 10Ashow side views of layered semiconductor structures, while FIGS. 8B, 9B,and 10B show corresponding top-down views of the respective structures.More specifically, FIGS. 8A and 8B show a last-metal (LM) layer 230,which may be similar to layer 10 described above with respect to FIG. 1.Arranged within the LM layer 230 are a contact pad 212 and a wire 215,which may be formed using conventional semiconductor processingtechniques (e.g., photolithographic patterning, etching, and metal fill)and which may be composed of conventional materials (e.g., copper,aluminum, alloys, etc.). The contact pad 212 and a wire 215 may have anydesired geometry within the scope of the invention.

As shown in FIGS. 9A and 9B, a capping layer 240 having a TV opening 217and a block 220 are formed over the LM layer 230, contact pad 212 andwire 215. In embodiments, the capping layer 240 may be similar tocapping layer 20 described with respect to FIG. 1, and may be formed bya blanket deposition of one or more layers of insulating material (e.g.,by CVD, etc.) followed by selective removal of portions of theinsulating material using conventional patterning and etching processes.The removal of portions of the capping layer 20 creates the TV opening217. As seen in FIG. 9B, a first portion of the contact pad 212 isexposed through the TV opening 217; however, the block 220 remains inplace over a second portion of the contact pad 212 such that the secondportion of the contact pad 212 is not exposed.

FIGS. 10A and 10B show a conductive layer 250 formed over the a cappinglayer 240 and in the TV opening 217 on exposed portions of the contactpad 212. In embodiments, the conductive layer 250 may be similar to pad30 described above with respect to FIG. 1 and may be formed usingconventional techniques (e.g., CVD, etc.) and materials (e.g.,aluminum). Although not shown, the semiconductor structure may befurther processed using conventional techniques, including forming apassivation layer, forming an FV opening in the passivation layer,forming a BLM or UBM layer in the FV opening and on exposed portions ofthe conductive layer 250, and forming a solder bump on the BLM or UBMlayer.

FIGS. 11-13 show perspective views of another embodiment of a contactpad 212′, wires 215′, and a conductive layer 250′ in accordance withfurther aspects of the invention. For explanatory purposes, FIGS. 11-13show only the conductive material and do not show insulating material(e.g., the LM layer, capping layer, passivation layer, etc.). Voids 260in the conductive layer 250′ represent where blocks (e.g., blocks 220)are arranged within the conductive layer 250′. As depicted in FIG. 13, aBLM layer 270 and solder bump 280 may be formed on the conductive layer250′, such that the contact pad 212′, conductive layer 250′, and BLMlayer 270 form a conductive path between the wires 215′ and the solderbump 280.

In accordance with aspects of the invention, the geometries of thecontact pad and via(s) extending from the contact pad to the nextconductive layer may be optimized to distribute the incoming currentprior to the base of the final via. In accordance with additionalaspects of the invention, the layer of aluminum (e.g., the aluminum pad)is eliminated from the TV and FV openings, and instead variouscombinations of copper pegs and plugs are arranged in the capping layerand the passivation layer. The copper pegs and plugs used inimplementations of the invention distribute current better than analuminum pad, and thus improve EM performance by reducing currentcrowding. Moreover, the use of copper pegs and plugs in embodiments ofthe invention, instead of a conventional aluminum pad, permitsplanarization of the top surface of the structure prior to UBM/BLMformation. Such planarization provides a smoother topology for theUBM/BLM and leads to improved yield and EM resistance. Additionally,elimination of the aluminum pad reduces process time and cost.

According to aspects of the invention described with respect to FIGS.14-40, the full width of the BLM layer (UBM capture pad) may contact thehighly conducting Cu metallization in the final via, which mitigates EMproblems by providing a better distribution of current flow into thesolder bump. Implementations of the invention provide a furtheradvantage over conventional aluminum pads in that Cu metallizationdemonstrates improved EM resistance compared to Al. Moreover, inembodiments, the planarization (e.g., CMP) of the Cu plated in the finalvia allows a smoother topology for the BLM layer (UBM capture pad)formation leading to improved yield and EM resistance. Furthermore, inembodiments, the thick Cu (e.g., greater than about 5 μm) plated in thefinal via and embedded in the thick spin-on polymeric dielectric acts asa buffer to any detrimental stresses on the underlying layers of low-kdielectric. Even further, implementations of the invention providesolder bump contact arrangements that are formed using less processingsteps.

FIGS. 14-22 show semiconductor structures and respective processingsteps of a solder bump contact arrangement in accordance with aspects ofthe invention. More specifically, FIG. 14 shows a layer 310, which maybe a last metal (LM) layer similar to layer 10 described with respect toFIG. 1. Included in the layer 310 is a contact pad 312 and one or morewires (not shown) that carry current to the contact pad 312. The contactpad 312 may have any suitable configuration, including a conventionalgeometry or a distributed configuration such as that described withrespect to FIGS. 4-13 of this disclosure. The contact pad 312 mayoptionally include one or more posts 317, which may be similar to posts17 described above with respect to FIG. 1. The contact pad 312 may beformed in the layer 310 using conventional processes (e.g.photolithographic patterning, etching, and metal fill) and materials(e.g., copper).

As shown in FIG. 15, a cap 319 is formed on the layer 310 and contactpad 312. In embodiments, the cap 319 is composed of silicon nitride orNBLoK (SiC(N,H)) deposited using conventional processes such as CVD,PECVD, ALD, etc. The cap 319 may have any desired thickness (e.g.,depth). The invention is not limited to the exemplary materials andprocesses described herein, and other materials and/or processes may beused to form the cap 319 within the scope of the invention.

As depicted in FIG. 16, a lower capping layer 322 is deposited on thecap 319. In embodiments, the lower capping layer 322 is composed of SiO₂and is deposited using conventional processes such as CVD, PECVD, etc.The lower capping layer 322 may have any desired thickness (e.g.,depth). The invention is not limited to the exemplary materials andprocesses described herein, and other materials and/or processes may beused to form the lower capping layer 322 within the scope of theinvention, such as atomic layer deposition (ALD) of other oxides.

As depicted in FIG. 17, an upper capping layer 323 is deposited on thelower capping layer 322. In embodiments, the upper capping layer 323 iscomposed of SiN and is deposited using conventional processes such asCVD, PECVD, ALD, etc. The upper capping layer 323 may have any desiredthickness (e.g., depth). The invention is not limited to the exemplarymaterials and processes described herein, and other materials and/orprocesses may be used to form the upper capping layer 323 within thescope of the invention, such as atomic layer deposition (ALD) of othernitrides.

In accordance with aspects of the invention, the cap 319, lower cappinglayer 322 and upper capping layer 323 constitute a capping layer 320. Inembodiments, the capping layer 320 may be formed of any number (e.g.,one or more) individual layers of hard dielectric material, and is notlimited to the configuration shown in FIGS. 14-17.

FIG. 18 shows a passivation layer 335 formed on the upper capping layer323. In embodiments, the passivation layer 335 is composed ofphotosensitive polyimide (PSPI) and is deposited using conventionalprocesses such as spin coating. The passivation layer 335 may be cured(e.g., baked) in order to complete the cross linking of the PSPI, as isknown such that further explanation is not believed necessary for anunderstanding of the invention. The passivation layer 335 may have anydesired thickness (e.g., depth). The invention is not limited to theexemplary materials and processes described herein, and other materialsand/or processes may be used to form the passivation layer 335 withinthe scope of the invention, such as curtain coating of other polymerpassivation materials.

As depicted in FIG. 19, in embodiments, a mask 360 is applied to the topof the passivation layer 335. The mask 360 is used to form an opening365 in the passivation layer 335. The mask 350 may be a photomask orhard mask that is created and patterned using conventional techniques.The opening 365 in the passivation layer 335 may be formed using anydesired material removal process, including but not limited to wet etch,dry etch, etc.

As depicted in FIG. 20, in embodiments, a second opening 370 is formedin the capping layer 320 (e.g., through upper capping layer 323, lowercapping layer 322, and cap 319) using the mask 360 and/or the patternedpassivation layer 335 as a mask. The second opening 370 may be formedusing any desired material removal technique, such as a reactive ionetch (RIE) that is selective to the materials of the capping layer 320but that does not etch the material of the contact pad 312. Moreover,although a two step process has been described for forming the opening365 and the second opening 370, a single material removal process may beused to form the opening 365 and the second opening 370 in a singleprocessing step. The mask 360 is removed using conventional strippingtechniques before or after the formation of the second opening 370.

In embodiments, the opening 365 in the passivation layer 335 and thesecond opening 370 in the capping layer 320 are substantially aligned(e.g., coaxial) and expose an upper surface of the contact pad 312. Inaccordance with aspects of the invention, the opening 365 and secondopening 370 may have any desired shape (e.g., in plan view), including,but not limited to substantially circular, oval, elliptical, square,rectangular, etc. Moreover, depending primarily on the material removalprocesses used, the sidewalls of the opening 365 and second opening 370may be substantially vertical or may arranged at a non-zero anglerelative to vertical.

Referring to FIG. 21, a conductive pedestal 375 is formed in the opening365 and second opening 370. In embodiments, the conductive pedestal 375is formed by selectively depositing a copper liner (e.g., copper seedlayer) on exposed surfaces of the opening 365 and second opening 370(e.g., on portions of the passivation layer 335, capping layer 320, andcontact pad 312), followed by copper plating and annealing. Inaccordance with aspects of the invention, the structure is planarizedafter formation of the conductive pedestal 375 using, for example, achemical mechanical polish (CMP). In this manner, a smooth topography isprovided for subsequent processing.

As shown in FIG. 22, a BLM layer 380 may be formed on the planarized topsurface of the conductive pedestal 375 and the passivation layer 335,and a solder bump 385 is formed on the BLM layer 380. In embodiments,the BLM layer 380 may comprise one or more layers, including but notlimited to a titanium-tungsten (TiW) layer directly on the conductivepedestal 375, a copper (Cu) layer on the TiW layer, and a nickel (Ni)layer on the Cu layer. However, the invention is not limited to such aBLM layer, and any suitable BLM layer may be used within the scope ofthe invention.

FIGS. 23-31 show semiconductor structures and respective processingsteps of a solder bump contact arrangement in accordance with additionalaspects of the invention. More specifically, the structure in FIG. 23includes a layer 310 in which a contact pad 312 is formed, a cap 319,and a lower capping layer 322.

As shown in FIG. 24, a TV opening 400 is formed in the lower cappinglayer 322 and the cap 319 to expose a portion of the contact pad 312.The TV opening 400 may be formed using any conventional techniques, suchas, for example, photolithographic masking and etching.

As depicted in FIG. 25, a trench 405 is formed in the lower cappinglayer 322. In embodiments, the trench 405 intersects the TV opening 400and extends only partially through the cap 319. The trench 405 may beformed using any conventional techniques, including but not limited to,photolithographic masking and etching.

As depicted in FIG. 26, a conductor 410 is formed in the TV opening 400and trench 405. In embodiments, the conductor 410 is formed bydepositing a copper liner (e.g., copper seed layer) on exposed surfacesof the TV opening 400 and trench 405, followed by copper plating, andannealing. In accordance with aspects of the invention, the structure isplanarized after formation of the conductor 410 using, for example, CMP.

FIG. 27 shows the formation of an upper capping layer 323 on the uppersurfaces of the conductor 410 and lower capping layer 322. The uppercapping layer 323 may be formed in a manner similar to that describedwith respect to FIG. 17.

FIG. 28 shows the formation of a passivation layer 335 on the uppercapping layer 323. The passivation layer 335 may be formed in a mannersimilar to that described with respect to FIG. 18.

As shown in FIG. 29, an FV opening 415 is formed in the passivationlayer 335 and upper capping layer 323. The FV opening 415 may be formedin a manner similar to the openings 365 and 370 described with respectto FIG. 19. In embodiments, the FV opening 415 is laterally offset fromthe TV opening 405, as depicted by the FV opening central axis “B” beingspaced apart from the TV opening central axis “C”.

As depicted in FIG. 30, a final via 420 is formed in the FV opening 415.In embodiments, the final via 420 is formed by depositing a copper liner(e.g., copper seed layer) on exposed surfaces of the FV opening 415,followed by copper plating and annealing. In accordance with aspects ofthe invention, the structure is planarized after formation of the finalvia 420, using for example, CMP.

As shown in FIG. 31, a BLM layer 380 and solder bump 385 are formed onthe structure. The BLM layer 380 is in contact with the final via 420.The BLM layer 380 and solder bump 385 may be formed in a manner similarto that described with respect to FIG. 22.

FIGS. 32-40 show semiconductor structures and respective processingsteps of a solder bump contact arrangement in accordance with otheraspects of the invention. More specifically, the structure in FIG. 32includes a layer 310 in which a contact pad 312 is formed. A cap 319, alower capping layer 322, and an upper capping layer 323 are formed overthe contact pad 312.

As depicted in FIG. 33, a TV opening 500 is formed in the cap 319, lowercapping layer 322, and upper capping layer 323. The TV opening 500exposes a portion of the contact pad 312. In embodiments, the TV opening500 may be formed using conventional processing techniques, includingbut not limited to photolithographic masking (e.g., patterning,exposing, and developing) and etching (e.g., RIE).

As depicted in FIG. 34, a terminal via 505 is formed in the TV opening500. In embodiments, the terminal via 505 is formed by depositing acopper liner (e.g., copper seed layer) on exposed surfaces of the TVopening 500, followed by copper plating and annealing. In accordancewith aspects of the invention, the structure is planarized afterformation of the terminal via 505, using for example, CMP.

Referring to FIG. 35, a barrier film 510 may be formed on the planarizedupper surfaces of the terminal via 505 and the upper capping layer 323.In embodiments, the barrier film 510 is composed of ultra-violet nitride(UVN) and is deposited using any suitable technique, such as CVD, PECVD,ALD, etc.

FIG. 36 shows the formation of a passivation layer 335 on the barrierfilm 510. The passivation layer 335 may be formed in a manner similar tothat described with respect to FIG. 18.

As shown in FIG. 37, an FV opening 515 is formed in the passivationlayer 335 and barrier film 510. The FV opening 415 may be formed in amanner similar to the openings 365 and 370 described with respect toFIG. 19. As depicted in FIG. 38, a final via 520 is formed in the FVopening 515. In embodiments, the final via 520 is formed by depositing acopper liner (e.g., copper seed layer) on exposed surfaces of the FVopening 515, followed by copper plating and annealing. In accordancewith aspects of the invention, the structure is planarized afterformation of the final via 520, using for example, CMP.

As shown in FIG. 39, a BLM layer 380 and solder bump 385 are formed onthe structure. The BLM layer 380 is in contact with the final via 520.The BLM layer 380 and solder bump 385 may be formed in a manner similarto that described with respect to FIG. 22.

In accordance with aspects of the invention, at the interface betweenthe final via 520 and the terminal via 505, the diameter of the finalvia 520 is smaller than a short edge of the terminal via 505. Forexample, as shown in FIG. 40, the terminal via 505 may have asubstantially rectangular shape having a long edge 530 and a short edge535. In embodiments, the lower portion 540 of the final via 520 iscontained within the footprint of the terminal via 505. In a particularexemplary embodiment, the long edge 530 is about 36 to 40 μm, the shortedge 535 is about 18 to 20 μm, and the diameter of the lower portion 540of the final via 520 is less than about 18 μm. The diameter of the upperportion of the final via 520 is not constrained relative to the terminalvia 505 and can be any desired value.

In accordance with further aspects of the invention, conductivestructures in the capping layer and passivation layer are optimized forspreading current in a solder bump contact arrangement. FIGS. 41-51 showsemiconductor structures and respective processing steps of a solderbump contact arrangement in accordance with additional aspects of theinvention. More specifically, the structure in FIG. 41 includes a layer310, a cap 319, a lower capping layer 322, and an upper capping layer323. The cap 319, lower capping layer 322, and upper capping layer 323collective form a hard dielectric capping layer 320. A contact pad 312is disposed in the layer 310, and one or more posts 317 may be arrangedwithin the contact pad 312.

As depicted in FIG. 42, a plurality of terminal vias 600 are formed inthe capping layer 320. In embodiments, the plurality of terminal vias600 may be formed using conventional processes, including, but notlimited to, masking and etching the capping layer 320 to form aplurality of terminal via openings, and depositing copper in theplurality of terminal via openings. The structure may be planarized,e.g., using CMP, after formation of the plurality of terminal vias.

FIG. 43 shows an exemplary arrangement of the plurality of terminal vias600 extending through the capping layer 320 down to the contact pad 312,with wires 315 shown connected to the contact pad 312. FIG. 44 showsanother exemplary arrangement of the plurality of terminal vias 600′extending through the capping layer 320 down to the contact pad 312,with wires 315 shown connected to the contact pad 312. The invention isnot limited to the exemplary arrangements shown herein, but rather,within the scope of the invention the plurality of vias may include anydesired number of vias having any desired geometry.

As depicted in FIG. 45, a passivation layer 335 is formed on the cappinglayer 320. The passivation layer 335 may be formed in a manner similarto that described with respect to FIG. 18. As depicted in FIG. 46, an FVopening 610 is formed in the passivation layer 335. The FV opening maybe formed using conventional processes, such as those described withrespect to FIG. 19.

As depicted in FIG. 47, a BLM layer 615 and a copper pedestal 620 areformed in the FV opening 610 in the passivation layer 335. Inembodiments, the copper pedestal 620 is formed using conventionalelectroplating process as is normally used for BLM/solder plating, suchthat further explanation is not believed necessary for completeunderstanding of the invention.

As shown in FIG. 48, a solder bump 625 is formed on the BLM layer 615.In accordance with aspects of the invention, the plurality of terminalvias 600 constitute a plurality of copper pegs that channel the currentto different portions of the BLM layer 615 and solder bump 625.

FIG. 49 shows a structure in accordance with aspects of the invention inwhich a plurality of terminal vias 600 are formed in the capping layer320 above and in contact with a contact pad 312 formed in a last metallayer 310. In embodiments, the plurality of terminal vias 600 are formedusing conventional processing techniques and are composed of copper. ACMP process is performed after forming the plurality of terminal vias600 but prior to forming the passivation layer 335. In accordance withaspects of the invention, a plurality of final vias 700 are formed inthe passivation layer 335 and in contact with the plurality of terminalvias 600. In embodiments, the plurality of final vias 700 are formedusing conventional processing techniques and are composed of copper. ACMP process is performed after forming the plurality of final vias 700but prior to forming the BLM layer 380 and the solder bump 385.

FIG. 50 shows a structure in accordance with additional aspects of theinvention in which a plug via 800 is formed in the capping layer 320above and in contact with a contact pad 312 formed in a last metal layer310. In embodiments, the plug via 800 is formed using conventionalprocessing techniques and is composed of copper. A CMP process isperformed after forming the plug via 800 but prior to forming thepassivation layer 335. In accordance with aspects of the invention, aplurality of final vias 700 are formed in the passivation layer 335 andin contact with the plug via 800. In embodiments, the plurality of finalvias 700 are formed using conventional processing techniques and arecomposed of copper. A CMP process is performed after forming theplurality of final vias 700 but prior to forming the BLM layer 380 andthe solder bump 385.

FIG. 51 shows a structure in accordance with aspects of the invention inwhich a plurality of terminal vias 600 are formed in the capping layer320 above and in contact with a contact pad 312 formed in a last metallayer 310. In embodiments, the plurality of terminal vias 600 are formedusing conventional processing techniques and are composed of copper. ACMP process is performed after forming the plurality of terminal vias600 but prior to forming the passivation layer 335. In accordance withaspects of the invention, a single final via 900 is formed in thepassivation layer 335 and in contact with the plurality of terminal vias600. In embodiments, the single final via 900 is formed usingconventional processing techniques and is composed of copper. A CMPprocess is performed after forming the single final via 900 but prior toforming the BLM layer 380 and the solder bump 385.

In accordance with further aspects of the invention, the currentspreading structures described herein can be used in conjunction withthe contact pad arrangements described herein. As but one example, thecontact pad 312 used in the configuration shown in FIG. 49 may besimilar to contact pad 100 described with respect to FIGS. 4 and 5 inthat it is comprised of a plurality of same-resistance wires.

According to aspects of the invention, the structures shown in FIGS.41-51 spread the current at the base of the BLM layer and/or C4 solderbump. Moreover, the structures are formed without a conventionalaluminum pad. In this manner, implementations of the invention enhanceEM resistance and enable optimal current input configuration at a baseof a BLM layer and/or C4 solder bump. Additionally, aspects of theinvention provide topographical planar surfaces (e.g., from CMP) withinthe plural layers of the structure. Such topographical planar surfacesare beneficial for current carrying capacity, and also are beneficialfor eliminating conventionally used structures, such as aluminum pads.

FIG. 52 shows a block diagram of an exemplary design flow 900 used forexample, in semiconductor IC logic design, simulation, test, layout, andmanufacture. Design flow 900 includes processes, machines and/ormechanisms for processing design structures or devices to generatelogically or otherwise functionally equivalent representations of thedesign structures and/or devices described above and shown in FIGS.4-51. The design structures processed and/or generated by design flow900 may be encoded on machine-readable transmission or storage media toinclude data and/or instructions that when executed or otherwiseprocessed on a data processing system generate a logically,structurally, mechanically, or otherwise functionally equivalentrepresentation of hardware components, circuits, devices, or systems.Machines include, but are not limited to, any machine used in an ICdesign process, such as designing, manufacturing, or simulating acircuit, component, device, or system. For example, machines mayinclude: lithography machines, machines and/or equipment for generatingmasks (e.g. e-beam writers), computers or equipment for simulatingdesign structures, any apparatus used in the manufacturing or testprocess, or any machines for programming functionally equivalentrepresentations of the design structures into any medium (e.g. a machinefor programming a programmable gate array).

Design flow 900 may vary depending on the type of representation beingdesigned. For example, a design flow 900 for building an applicationspecific IC (ASIC) may differ from a design flow 900 for designing astandard component or from a design flow 900 for instantiating thedesign into a programmable array, for example a programmable gate array(PGA) or a field programmable gate array (FPGA) offered by Altera® Inc.or Xilinx® Inc.

FIG. 52 illustrates multiple such design structures including an inputdesign structure 920 that is preferably processed by a design process910. Design structure 920 may be a logical simulation design structuregenerated and processed by design process 910 to produce a logicallyequivalent functional representation of a hardware device. Designstructure 920 may also or alternatively comprise data and/or programinstructions that when processed by design process 910, generate afunctional representation of the physical structure of a hardwaredevice. Whether representing functional and/or structural designfeatures, design structure 920 may be generated using electroniccomputer-aided design (ECAD) such as implemented by a coredeveloper/designer. When encoded on a machine-readable datatransmission, gate array, or storage medium, design structure 920 may beaccessed and processed by one or more hardware and/or software moduleswithin design process 910 to simulate or otherwise functionallyrepresent an electronic component, circuit, electronic or logic module,apparatus, device, or system such as those shown in FIGS. 4-51. As such,design structure 920 may comprise files or other data structuresincluding human and/or machine-readable source code, compiledstructures, and computer-executable code structures that when processedby a design or simulation data processing system, functionally simulateor otherwise represent circuits or other levels of hardware logicdesign. Such data structures may include hardware-description language(HDL) design entities or other data structures conforming to and/orcompatible with lower-level HDL design languages such as Verilog andVHDL, and/or higher level design languages such as C or C++.

Design process 910 preferably employs and incorporates hardware and/orsoftware modules for synthesizing, translating, or otherwise processinga design/simulation functional equivalent of the components, circuits,devices, or logic structures shown in FIGS. 4-51 to generate a netlist980 which may contain design structures such as design structure 920.Netlist 980 may comprise, for example, compiled or otherwise processeddata structures representing a list of wires, discrete components, logicgates, control circuits, I/O devices, models, etc. that describes theconnections to other elements and circuits in an integrated circuitdesign. Netlist 980 may be synthesized using an iterative process inwhich netlist 980 is resynthesized one or more times depending on designspecifications and parameters for the device. As with other designstructure types described herein, netlist 980 may be recorded on amachine-readable data storage medium or programmed into a programmablegate array. The medium may be a non-volatile storage medium such as amagnetic or optical disk drive, a programmable gate array, a compactflash, or other flash memory. Additionally, or in the alternative, themedium may be a system or cache memory, buffer space, or electrically oroptically conductive devices and materials on which data packets may betransmitted and intermediately stored via the Internet, or othernetworking suitable means.

Design process 910 may include hardware and software modules forprocessing a variety of input data structure types including netlist980. Such data structure types may reside, for example, within libraryelements 930 and include a set of commonly used elements, circuits, anddevices, including models, layouts, and symbolic representations, for agiven manufacturing technology (e.g., different technology nodes, 32 nm,45 nm, 90 nm, etc.). The data structure types may further include designspecifications 940, characterization data 950, verification data 960,design rules 970, and test data files 985 which may include input testpatterns, output test results, and other testing information. Designprocess 910 may further include, for example, standard mechanical designprocesses such as stress analysis, thermal analysis, mechanical eventsimulation, process simulation for operations such as casting, molding,and die press forming, etc. One of ordinary skill in the art ofmechanical design can appreciate the extent of possible mechanicaldesign tools and applications used in design process 910 withoutdeviating from the scope and spirit of the invention. Design process 910may also include modules for performing standard circuit designprocesses such as timing analysis, verification, design rule checking,place and route operations, etc.

Design process 910 employs and incorporates logic and physical designtools such as HDL compilers and simulation model build tools to processdesign structure 920 together with some or all of the depictedsupporting data structures along with any additional mechanical designor data (if applicable), to generate a second design structure 990.Design structure 990 resides on a storage medium or programmable gatearray in a data format used for the exchange of data of mechanicaldevices and structures (e.g. information stored in a IGES, DXF,Parasolid XT, JT, DRG, or any other suitable format for storing orrendering such mechanical design structures). Similar to designstructure 920, design structure 990 preferably comprises one or morefiles, data structures, or other computer-encoded data or instructionsthat reside on transmission or data storage media and that whenprocessed by an ECAD system generate a logically or otherwisefunctionally equivalent form of one or more of the embodiments of theinvention shown in FIGS. 4-51. In one embodiment, design structure 990may comprise a compiled, executable HDL simulation model thatfunctionally simulates the devices shown in FIGS. 4-51.

Design structure 990 may also employ a data format used for the exchangeof layout data of integrated circuits and/or symbolic data format (e.g.information stored in a GDSII (GDS2), GL1, OASIS, map files, or anyother suitable format for storing such design data structures). Designstructure 990 may comprise information such as, for example, symbolicdata, map files, test data files, design content files, manufacturingdata, layout parameters, wires, levels of metal, vias, shapes, data forrouting through the manufacturing line, and any other data required by amanufacturer or other designer/developer to produce a device orstructure as described above and shown in FIGS. 4-51. Design structure990 may then proceed to a stage 995 where, for example, design structure990: proceeds to tape-out, is released to manufacturing, is released toa mask house, is sent to another design house, is sent back to thecustomer, etc.

The method as described above is used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, whereapplicable, are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed. The description of the present invention has beenpresented for purposes of illustration and description, but is notintended to be exhaustive or limited to the invention in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art without departing from the scope and spiritof the invention. The embodiment was chosen and described in order tobest explain the principles of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand the invention for various embodiments with variousmodifications as are suited to the particular use contemplated.Accordingly, while the invention has been described in terms ofembodiments, those of skill in the art will recognize that the inventioncan be practiced with modifications and in the spirit and scope of theappended claims.

What is claimed is:
 1. A semiconductor structure, comprising: a contactpad in a last wiring level of a chip; and a plurality of wires of thecontact pad extending from side edges of the contact pad to respectiveones of a plurality of vias, wherein each one of the plurality of wireshas substantially the same electrical resistances and at least two ofthe plurality of wires comprise different widths and different lengths.2. The semiconductor structure of claim 1, wherein the plurality ofwires are formed from the contact pad.
 3. The semiconductor structure ofclaim 1, wherein at least one of the plurality of wires widens at alocation adjacent a leading edge of a respective one of the plurality ofvias.
 4. A semiconductor structure, comprising: a contact pad in a lastwiring level of a chip; and a plurality of wires of the contact padextending from side edges of the contact pad to respective ones of aplurality of vias, wherein: each one of the plurality of wires hassubstantially the same electrical resistance, a first one of theplurality of wires has a first length and a first width, a second one ofthe plurality of wires has a second length and a second width, the firstwidth is different from the second width, and the first length isdifferent from the second length.
 5. The semiconductor structure ofclaim 4, further comprising: a capping layer on the last wiring level ofthe chip; a passivation layer on the capping layer; at least one finalvia in the passivation layer; a ball limiting metallurgy (BLM) layer onthe at least one final via and the passivation layer; and a solder bumpon the BLM layer.
 6. The semiconductor structure of claim 3, wherein:the plurality of vias are disposed in the capping layer; the pluralityof vias and the capping layer have substantially coplanar uppersurfaces; and the at least one final vias and the passivation layer havesubstantially coplanar upper surfaces.
 7. A semiconductor device,comprising: a solder bump contact pad in a last wiring level of a chip;at least one wire in the last wiring level, wherein the at least onewire contacts the solder bump contact pad; a dielectric capping layerformed on the last wiring level, the solder bump contact pad, and the atleast one wire; and an opening in the dielectric capping layer, whereinthe opening exposes a portion of an upper surface of the solder bumpcontact pad and defines at least one block, wherein the at least oneblock comprises residual material of the dielectric capping layer on aportion of the solder bump contact pad, and the at least one blocksurrounds a location where the at least one wire contacts the solderbump contact pad.
 8. The semiconductor device of claim 7, furthercomprising a conductive layer formed in the opening and on the exposedportion of the solder bump contact pad.
 9. The semiconductor device ofclaim 8, further comprising: a ball limiting metallurgy (BLM) layerformed on the conductive layer; and a solder bump formed on the BLMlayer, wherein the at least one block causes current entering the solderbump contact pad from the at least one wire to flow laterally within thesolder bump contact pad beyond an area defined by the at least oneblock.
 10. The semiconductor device of claim 7, wherein: the at leastone wire is formed as a plurality of wires; and the at least one blockis formed as a plurality of blocks; wherein respective ones of theplurality of blocks contact and cover respective locations of the solderbump contact pad where respective ones of the plurality of wires contactthe solder bump contact pad.
 11. A semiconductor device, comprising: acapping layer formed on a solder bump contact pad that is arranged in alast wiring level of a chip; a passivation layer formed on the cappinglayer; a terminal via formed in the capping layer, wherein the terminalvia contacts the solder bump contact pad; a final via formed in thepassivation layer, wherein the final via is in electrical contact withthe terminal via; a ball limiting metallurgy (BLM) layer formed on uppersurfaces of the final via and the passivation layer; and a solder bumpformed on the BLM layer, wherein the solder bump contact pad comprises aplurality of wires, which extend from side edges of the solder bumpcontact pad to respective ones of a plurality of vias, and each one ofthe plurality of wires has substantially the same electrical resistance.12. The semiconductor device of claim 11, wherein the upper surfaces ofthe final via and the passivation layer are co-planar.
 13. Thesemiconductor device of claim 11, wherein a central axis of the finalvia is laterally offset from a central axis of the terminal via.